The present invention relates generally to direct-viewing bistable storage tubes, and more particularly to an improved method for erasing images stored by such tubes.
Direct-viewing bistable storage tubes, which will also be referred to below as DVST's or simply "storage tubes," have achieved significant commerical success as information display devices for computers. One of the principal advantages of DVST's in this application is their ability to store and display information indefinitely. This eliminates the need for periodic display refreshment by the computer or by dedicated refresh circuitry provided within the display unit.
User demands for greater display capacity have led to the development of larger and larger size storage tubes. Over the past 15 years, for example, commercially available DVST's have increased in display screen area from a maximum of 80 cm.sup.2 in 1962 to 1770 cm.sup.2 today. The larger size display screens have seriously aggravated an already annoying characteristic of conventional storage tube operation--a bright flash that occurs when the entire display screen is momentarily brightly illuminated during the image erase cycle. The flash from a 19 in. or 25 in. storage tube is very hard on a viewer's eyes, particularly when the display unit is used in a darkened room.
Accordingly, a general object of the present invention is to provide an improved method of erasing information stored by a direct-viewing bistable storage tube.
A more specific object of the invention is to provide an improved method of operating a DVST to minimize or eliminate the bright flash that accompanies the standard erase cycle.
Another object of the invention is to provide an improved DVST erase cycle that minimizes or eliminates the usual bright flash without adversely affecting the storage tube's operating or image display characteristics.
Still another object of the invention is to provide an improved DVST erase cycle of reduced overall length.
A further object is to provide an improved DVST erase method that minimizes the production of dark residual images.